There are a number of United States patents assigned to Petro-Tex Chemical Corporation issued in the late 1960's that disclose the use of various ferrites in a steam cracker to produce olefins from paraffins. The patents include U.S. Pat. Nos. 3,420,911 and 3,420,912 in the names of Woskow et al. The patents teach the use of ferrites such as zinc, cadmium, and manganese ferrites (i.e., mixed oxides with iron oxide) in oxidative dehydrogenation. The ferrites are introduced into a dehydrogenation zone at a temperature from about 250° C. up to about 750° C. at pressures less than 100 psi (689 kPa) for a time less than 2 seconds, typically, from 0.005 to 0.9 seconds. The reaction appears to take place in the presence of steam that may tend to shift the equilibrium in the “wrong” direction. Additionally, the reaction takes place in the presence of a catalyst not of the present invention.
In the Petro-Tex patents, the metal ferrite (e.g., MFeO4 where, for example, M is Mg, Mn, Co, Ni, Zn or Cd) is circulated through the dehydrogenation zone and then to a regeneration zone where the ferrite is reoxidized and then fed back to the dehydrogenation zone.
The Great Britain Patent No. 1,213,181, which seems to correspond in part to the above Petro-Tex patents, discloses that nickel ferrite may be used in the oxidative dehydrogenation process. The reaction conditions are comparable to those of above noted Petro-Tex patents.
U.S. Pat. No. 6,891,075 issued May 10, 2005 to Liu, assigned to Symyx Technologies, Inc. teaches a catalyst for the oxidative dehydrogenation of a paraffin (alkane) such as ethane. The gaseous feedstock comprises at least the alkane and oxygen, but may also include diluents (such as, argon, nitrogen, etc.) or other components (such as, water or carbon dioxide). The dehydrogenation catalyst comprises at least about 2 weight % of NiO and a broad range of other elements, preferably, Nb, Ta, and Co. While NiO is present in the catalyst, it does not appear to be the source of the oxygen for the oxidative dehydrogenation of the alkane (ethane).
U.S. Pat. No. 6,521,808 issued Feb. 18, 2003 to Ozkan, et al, assigned to the Ohio State University teaches sol gel supported catalysts for the oxidative dehydrogenation of ethane to ethylene. The catalyst appears to be a mixed metal system, such as, Ni—Co—Mo, V—Nb—Mo possibly doped with small amounts of Li, Na, K, Rb, and Cs on a mixed silica oxide/titanium oxide support. The catalyst does not provide the oxygen for the oxidative dehydrogenation, rather, gaseous oxygen is included in the feed.
U.S. Pat. No. 4,450,313, issued May 22, 1984 to Eastman et al., assigned to Phillips Petroleum Company, discloses a catalyst of the composition Li2O—TiO2, which is characterized by a low ethane conversion not exceeding 10%, in spite of a rather high selectivity to ethylene (92%). The major drawback of this catalyst is the high temperature of the process of oxidative dehydrogenation, which is close to or higher than 650° C.
The preparation of a supported catalyst useful for low-temperature oxidative dehydrogenation of ethane to ethylene is disclosed in the U.S. Pat. No. 4,596,787 A issued Jun. 24, 1986 to Manyik et al., assigned to Union Carbide Corporation. A supported catalyst for the low-temperature gas-phase oxidative dehydrogenation of ethane to ethylene is prepared by (a) preparing a precursor solution having soluble and insoluble portions of metal compounds, (b) separating the soluble portion, (c) impregnating a catalyst support with the soluble portion and (d) activating the impregnated support to obtain the catalyst. The calcined catalyst has the compositionMoaVbNbcSbdXe wherein X is nothing or Li, Sc, Na, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Y, Ta, Cr, Fe, Co, Ni, Ce, La, Zn, Cd, Hg, Al, Tl, Pb, As, Bi, Te, U, Mn and/or W; a is 0.5-0.9; b is 0.1-0.4; c is 0.001-0.2; d is 0.001-0.1; and e is 0.001-0.1 when X is an element. The patent fails to teach or suggest a co-commination of the catalyst and the support.
Other examples of the low temperature oxidative dehydrogenation of ethane to ethylene using a calcined oxide catalyst containing molybdenum, vanadium, niobium and antimony are described in U.S. Pat. No. 4,524,236 A, issued Jun. 18, 1985 and U.S. Pat. No. 4,250,346 A, issued Feb. 10, 1981, both assigned to Union Carbide Corporation. The calcined catalyst containsMoaVbNbcSbdXe in the form of oxides. The catalyst is prepared from a solution of soluble compounds and/or complexes and/or compounds of each of the metals. The dried catalyst is calcined by heating at 220 to 550° C. in air or oxygen. The catalyst precursor solutions may be supported onto an inorganic oxide (e.g., silica, aluminum oxide, silicon carbide, zirconia, titania or mixtures of these). The selectivity to ethylene may be greater than 65% for a 50% conversion of ethane.
The U.S. Pat. No. 6,624,116, issued Sep. 23, 2003 to Bharadwaj, et al. and U.S. Pat. No. 6,566,573 issued May 20, 2003 to Bharadwaj, et al., both assigned to Dow Global Technologies Inc., disclose Pt—Sn—Sb—Cu—Ag monolith systems that have been tested in an auto-thermal regime at T>750° C. where the starting gas mixture contains hydrogen (H2: O2=2:1, gas hourly space velocity (GHSV) of 180 000 h−1). The catalyst composition is different from that of the present invention and the present invention does not contemplate the use of molecular hydrogen in the feed.
U.S. Pat. No. 4,524,236 issued Jun. 18, 1985 to McCain assigned to Union Carbide Corporation and U.S. Pat. No. 4,899,003, issued Feb. 6, 1990 to Manyik et al. assigned to Union Carbide Chemicals and Plastics Company Inc. disclose mixed metal oxide catalysts of V—Mo—Nb—Sb. At 375 to 400° C. the ethane conversion reached 70% with the selectivity close to 71 to 73%. However, this ethane conversion result was only achieved at very low gas hourly space velocities (i.e., 720 h−1).
U.S. Pat. No. 7,319,179 issued Jan. 15, 2008 to Lopez-Nieto et al. assigned to Consejo Superior de Investigaciones Cientificas and Universidad Politecnica de Valencia discloses Mo—V—Te—Nb—O oxide catalysts that provided an ethane conversion of 50-70% and selectivity to ethylene up to 95% (at 38% conversion) at 360 to 400° C. The catalysts have the empirical formulaMoTehViNbjAkOx where A is a fifth modifying element. The catalyst is a calcined mixed oxide (at least of Mo, Te, V and Nb), optionally supported on: (i) silica, alumina and/or titania, preferably silica at 20 to 70 wt % of the total supported catalyst or (ii) silicon carbide. The supported catalyst is prepared by conventional methods of precipitation from solutions, drying the precipitate and then calcining.
The preparation of a Mo—Te—V—Nb composition is described in WO 2005058498 A1, published 30 Jun. 2005 (corresponding to U.S. Published Application No. 2007149390 A1). Preparation of the catalyst involves preparing a slurry by combining an inert ceramic carrier with at least one solution comprising ionic species of Mo, V, Te, and Nb, drying the slurry to obtain a particulate product, precalcining the dried product at 150 to 350° C. in an oxygen-containing atmosphere and calcining the dried product at 350 to 750° C. under inert atmosphere. The catalyst prepared exhibits the activity and selectivity in the oxidation reaction comparable to the non-supported catalyst.
A process for manufacturing ethylene from gaseous feed comprising ethane and oxygen involving contacting the feed with a mixed oxide catalyst containing vanadium, molybdenum, tantalum and tellurium in a reactor to form an ethylene-containing effluent is disclosed in WO 2006130288 A1, published Dec. 7 2006, (also, published Sep. 2, 2010 as U.S. Published Application No. 20100222623, now abandoned) assigned to Celanese Int. Corp. The catalyst has a selectivity for ethylene of 50 to 80% thereby allowing oxidation of ethane to produce ethylene and acetic acid with high selectivity. The catalyst has the formulaMo1V0.3Ta0.1Te0.3Oz.The catalyst is optionally supported on an inorganic oxide supported on a support selected from porous silicon dioxide, ignited silicon dioxide, kieselguhr, silica gel, porous and nonporous aluminum oxide, titanium dioxide, zirconium dioxide, thorium dioxide, lanthanum oxide, magnesium oxide, calcium oxide, barium oxide, tin oxide, cerium dioxide, zinc oxide, boron oxide, boron nitride, boron carbide, boron phosphate, zirconium phosphate, aluminum silicate, silicon nitride, silicon carbide, and glass, carbon, carbon-fiber, activated carbon, metal-oxide or metal networks and corresponding monoliths, or is encapsulated in, preferably, silicon dioxide (SiO2), phosphorus pentoxide (P2O5), magnesium oxide (MgO), chromium trioxide (Cr2O3), titanium oxide (TiO2), zirconium oxide (ZrO2) or alumina (Al2O3). The methods of preparation of the supported compositions involve the procedures of wet chemistry (solutions are impregnated into the solid support and then the materials are dried and calcined).
U.S. Pat. No. 5,202,517 issued Apr. 13, 1993 to Minet et al., assigned to Medalert Incorporated, teaches a ceramic tube for use in the conventional dehydrogenation of ethane to ethylene. The “tube” is a ceramic membrane in which the ethane flows inside the tube and hydrogen diffuses out of the tube to improve the reaction kinetics. The reactive ceramic is 5 micrometers thick on a 1.5 to 2 mm thick support.
U.S. Pat. No. 6,818,189 issued Nov. 16, 2004 to Adris et al., assigned to Saudi Basic Industries Corporation, teaches a process in which ceramic pellets are packed around a tubular reactor and different reactants flow around the outside and inside of the tube. The patent is directed to the oxidative dehydrogenation of ethane to ethylene.
There is a significant amount of art on the separation of ethylene and ethane using silver or copper ions in their +1 oxidation state. See U.S. Pat. No. 6,518,476 issued Feb. 11, 2003 to Culp et al. assigned to Union Carbide Chemicals & Plastics Technology Corporation at Col. 5, lines 10-15 and Col. 16, line 12 to Col. 17, line 57. NOVA Chemicals Corporation has also disclosed separation of olefins from non-olefins using ionic liquids (dithiolene in CA 2415064, now abandoned). Also see U.S. Pat. No. 6,120,692 issued Sep. 19, 2000 to Wang et al., assigned to Exxon Research and Engineering Company, the abstract of JP 59172428 published Sep. 29, 1984 and the abstract of JP 59172427 published Sep. 29, 1984.
U.S. Pat. No. 8,017,825 issued Sep. 13, 2011 to Kuznicki et al. assigned to the Governors of the University of Alberta contains a good outline of prior art for separation of ethane from ethylene and an adsorption method using modified ETS-10.
U.S. Pat. No. 7,411,107 issued Aug. 12, 2008 to Lucy et al., assigned to BP Chemicals Limited discloses a process for the separation of acetic acid from an oxidative dehydrogenation process to convert ethane to ethylene and acetic acid. The process uses a reversible complex of a metal salt (e.g., Cu or Ag) to separate ethylene (Col. 8). The patent then discloses the acetic acid may be separated from the liquids by a distillation (Col. 13, lines 35-40).
U.S. Published Application No. 20110245571 in the name of NOVA Chemicals (International) S.A. teaches oxidative dehydrogenation of ethane in a fluidized bed in contact with a bed of regenerative oxides to provide oxygen to the reactor. In this process, free oxygen is not directly mixed with the feedstock reducing the likelihood of decompositions.
U.S. Pat. No. 3,904,703 issued Sep. 9, 1975 to Lo et al., assigned to El Paso Products Company teaches a zoned or layered oxidative reactor in which following a zone for oxidative dehydrogenation there is an “oxidation zone” following a dehydrogenation zone to oxidize the hydrogen to water. Following the oxidation zone there is an adsorption bed to remove water from the reactants before they enter a subsequent dehydrogenation zone. This is to reduce the impact of water on downstream dehydrogenation catalysts.
U.S. Published Application No. 20100256432 published Oct. 7, 2010 in the name of Arnold et al., assigned to Lummus discloses in paragraphs 86-94 methods to remove residual oxygen from the product stream. A combustible such as hydrogen or a hydrocarbon may be added to the product stream to eliminate residual oxygen. The patent refers to a catalyst but does not disclose its composition. As noted above, it may then be necessary to treat the product stream to eliminate water.
U.S. Pat. No. 6,518,476 issued Feb. 11, 2003 to Culp et al., assigned to Union Carbide Chemicals & Plastics Technology Corporation discloses a process for coupling lower paraffins, such as, methane and then oxidative dehydrogenation of the coupled product to produce olefins such as ethylene and propylene.
None of the above art teaches or suggests a chemical complex in which intermediate a cracker and a separation train there is an oxidative dehydrogenation process.
The present invention seeks to provide a novel chemical complex in which there is an oxidative dehydrogenation process to dehydrogenate ethane to ethylene intermediate a chemicals cracker (e.g., a steam cracker) and the associated downstream separation units. This will provide expansion capacity at reduced operating costs. More particularly, in one aspect the overheads from the C2 splitter could be passed through the oxidative dehydrogenation unit to reduce the ethane content (polish the product stream). In some cases, the upper portion of the rectifying portion of the C2 splitter is used to reduce very low amounts of residual ethane in the ethylene. The technology of the present patent application may be applied to a new ethylene manufacturing site (greenfield development) or could be a retrofit to an existing facility to expand capacity at a minimum cost.